Catheter having a reinforcing mandrel

ABSTRACT

A catheter having a mandrel secured to the catheter or constrained within a dedicated lumen. In one embodiment, the catheter has an inner tubular member and an outer tubular member with a sidewall configured to define a mandrel lumen longitudinally along an inner surface of the outer tubular member or along an outer surface of the inner tubular member. The mandrel lumen may be configured to allow the mandrel to be exchanged to adjust the handling characteristics of the catheter. The mandrel may occupy an intermediate portion of the catheter shaft, or may extend from the proximal end to within proximal or distal shaft sections of the catheter. In coronary artery applications, the mandrel is configured to support the catheter as it bends through the aortic arch and enters the coronary artery.

BACKGROUND OF THE INVENTION

This invention relates to the field of medical devices, and moreparticularly to a balloon catheter having a reinforcing mandrel.

Catheters designed for intravascular procedures such as angioplasty havea number of desirable characteristics. Such catheters must be able totransmit force along the length of the catheter shaft to allow it to bepushed through the vasculature. However, the catheter shaft must alsoretain sufficient flexibility to allow it to track over a guidewirethrough the often tortuous vasculature. Additionally, the catheter alsomust be able to cross stenosed portions of the vascular anatomy.

To help meet the desire for a catheter having sufficient pushability andcrossability, while maintaining trackability, prior art designs havesupplemented polymer catheter shafts with a stiffening wire or mandrel.Other prior art designs have addressed these handling and performanceissues by using materials of different stiffness for the proximal anddistal portions of the catheter, and employing a high strength metallicproximal shaft section, commonly called a hypotube. To prevent kinkingat the junction of these two materials, while maintaining trackabilityand pushability, some conventional designs have employed a stiffeningwire to bridge the transition in catheter shaft material. Despite theseattempts, prior art designs have suffered from various drawbacks. Forexample, support mandrels do not always transmit axial forceeffectively.

Accordingly, it would be a significant advance to provide a catheterhaving improved pushability and crossability while maintaining goodtrackability. This invention satisfies these and other needs.

SUMMARY OF THE INVENTION

The invention is directed to catheters having supporting mandrels toimprove pushability and trackability. The mandrel is constrained withinthe catheter shaft by being located within a dedicated mandrel lumen orsecured at least in part directly to the catheter shaft. The length andposition of the mandrel Within the catheter shaft may vary, so that themandrel extends distally from the proximal end of the catheter shaft, oralternatively, from a location distal to the proximal end of thecatheter shaft. The term mandrel should be understood to include avariety of different supporting members such as solid or hollow rods,wires, and the like.

One embodiment of the catheter of the invention comprises an innertubular member defining a guidewire lumen and an outer tubular membercoaxially or eccentrically disposed about the inner tubular member toform an annular inflation lumen, with a side wall which extendslongitudinally within the annular inflation lumen and which defines amandrel lumen configured to receive a mandrel therein. In a presentlypreferred embodiment, the sidewall extends along at least a portion ofan inner surface of the outer tubular member. However, the sidewall mayalternatively extend along at least a portion of an outer surface of theinner tubular member. The reinforcement provided by the mandrel improvespushability and columnar strength of the catheter shaft formed fromrelatively soft materials, while inhibiting or preventing shaft kinking.This aids manufacturing by offering better bonding to balloon materialsand allows greater flexibility in catheter design. These designs alsopermit a reduction in wall thickness to maximize the inflation lumen.The mandrel lumen may be configured to allow the mandrel to be exchangedto adjust the handling characteristics of the catheter. Thus, in oneembodiment, the mandrel lumen extends to the proximal end of the shaftto facilitate mandrel exchange. Alternatively, the mandrel may besecured within the lumen, at one or more points on the mandrel.

Another embodiment comprises a mandrel having a proximal end distal tothe proximal end of the catheter shaft. In a presently preferredembodiment, the mandrel is in an intermediate portion of the shaftbetween proximal and distal shaft portions. The intermediate portiontypically has a length less than the length of the proximal or thedistal shaft sections. The mandrel may be within a sidewall portiondefining a mandrel lumen or alternatively, may be secured to thecatheter shaft at the proximal and distal ends of the mandrel, or alongthe length thereof from the proximal to the distal end of the mandrel.In a presently preferred embodiment, the mandrel is within the lumen ofa side wall which extends longitudinally along at least a portion of aninner surface of the outer tubular member. The proximal and distalportions of the outer tubular member have conventional profiles, andform the inflation lumen in conjunction with the coaxial inner tubularmember. The intermediate portion has a sidewall portion configured todefine a mandrel lumen along its inner surface. The mandrel is typicallysecured within the lumen, preferably by heat deformation. In coronaryartery applications, the mandrel is configured to support the catheteras it bends through the aortic arch and enters the coronary artery.Preferably, the portion of the catheter carrying the mandrel does notenter the coronary artery.

In other embodiments, the mandrel is secured along the length of themandrel from the proximal to the distal end thereof directly to theinner tubular member or to the outer tubular member, without a sidewallmandrel lumen. In another embodiment, the catheter has rapid exchangecapabilities and generally comprises an elongated proximal tubularmember having a sidewall configured to define a mandrel lumen extendinglongitudinally along an inner surface of the proximal tubular member. Aninner tubular member overlaps the distal portion of the proximal tubularmember and provides a guidewire lumen with guidewire entry and exitports. A distal tubular member secures the adjacent portions of theproximal tubular member and the inner tubular member and carries aballoon, such as a dilatation balloon, on the distal end. The supportmandrel is disposed within the mandrel lumen. Restraining the supportmandrel within the lumen provides superior transmission of axial forcesto improve pushability. Moreover, the dedicated lumen addresses failureconcerns by allowing the catheter to be withdrawn intact in case of amandrel fracture. When the mandrel is not confined to a dedicated lumen,a fractured end could penetrate the catheter shaft or otherwise preventits easy removal through the tortuous vasculature.

The catheter of the invention having a mandrel has excellentcrossability and trackability. The mandrel connected to the cathetershaft directly or within the dedicated mandrel lumen provides effectivetransmission of axial force and avoids the entanglement of the mandrelaround the inner tubular member by preventing movement of the mandrelwithin the annular lumen. The catheter of the invention also has a lowprofile shaft design, and provides suitable stiffness transitionsbetween proximal and distal portions of the catheter to improve handlingand performance and minimize kinking. These and other advantages of theinvention will become more apparent from the following detaileddescription and exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of a ballooncatheter which embodies features of the invention, having a dedicatedmandrel lumen along an inner surface of the outer tubular member.

FIG. 2 is a cross sectional view of the catheter shown in FIG. 1, takenalong lines 2—2.

FIG. 3 is a cross sectional view of the catheter shown in FIG. 1, takenlong lines 3—3.

FIG. 4 is a cross sectional view of an alternate embodiment of thecatheter of the invention, having a mandrel lumen defined by a sidewallsecured to the outer tubular member along a transverse length of thesidewall which is less than the diameter of the side wall.

FIG. 5 is a cross sectional view of an alternate embodiment showing thesupport mandrel secured directly to the outer tubular member.

FIG. 6 is a cross sectional view of an alternate embodiment showing thesupport mandrel secured directly to the inner tubular member.

FIG. 7 is a cross sectional view of an alternate embodiment having asupport mandrel lumen on an outer surface of an inner tubular member.

FIG. 8 is a cross sectional view of a prior art catheter having asupport mandrel.

FIG. 9 is a schematic view of an embodiment of the invention whichembodies features of the invention, having an intermediate supportmandrel.

FIG. 10 is an enlarged view of the catheter shown in FIG. 9, takenwithin area 10.

FIG. 11 is a cross sectional view taken along lines 11—11.

FIG. 12 is a schematic view of a catheter of the invention whichembodies features of the invention, having rapid exchange capabilities.

FIG. 13 is a cross sectional view of the catheter shown in FIG. 12 takenalong lines 13—13.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a balloon catheter 10 embodying features of theinvention, having a proximal shaft portion 11, a distal shaft portion 12which is typically more flexible than proximal shaft portion 11, aninner tubular member 13, and an outer tubular member 14. Inner tubularmember 13 has a guidewire port 16 at its distal end and defines aguidewire lumen 18 configured to receive guidewire 20, as bestillustrated in FIGS. 2 and 3, showing transverse cross sections of thecatheter shaft taken along lines 2—2 and 3—3, respectively. Outertubular member 14 is coaxially disposed about inner tubular member 13creating annular inflation lumen 22. A balloon 24, preferably suitablefor performing an angioplasty procedure has a proximal, end disposedabout and secured to a distal portion of outer tubular member 14, adistal end disposed about and secured to a distal portion of the innertubular member 13, and an interior in fluid communication with inflationlumen 22. Adapter 26 at the proximal end of catheter 10 providesfittings for access to inflation lumen 22 and guidewire lumen 18. Asidewall 28 extends longitudinally along an interior surface of outertubular member 14, and is configured to define a mandrel lumen 30. Amandrel 32 is disposed within mandrel lumen 30.

Sidewall 28 extends from the proximal end of the catheter shaft along atleast a section of the proximal shaft section 11. In a presentlypreferred embodiment, sidewall 28 distal end extends within the proximalshaft portion 11. However, sidewall 28 may extend within the distalshaft portion 12. In the embodiment illustrated in FIG. 1, the sidewall28 extends within at least a section of the distal shaft portion 12. Thelength of the sidewall 28, and mandrel 32 therein, is about 2% to about35% less than, and preferably about 15% to about 30% less than thelength of the inner tubular member 13. The sidewall 28 and mandrel 32are typically about 50 cm to about 140 cm long, preferably about 100 cmto about 120 cm long, for a balloon catheter of about 145 cm in length.For coronary artery applications, the mandrel 32 preferably extendsthrough the proximal portion of the catheter so that it providesreinforcement and transmission of push through the aortic arch, butgenerally does not extend into the section of the catheter which extendswithin the coronary artery.

The diameter of mandrel 32 may be adjusted as desired to achieve thedesired handling characteristics, but generally should be about 0.005 toabout 0.015 inch. Preferably, the mandrel lumen 30 has an inner diameternot substantially larger than the diameter of the mandrel, i.e., about10% to about 30%, preferably about 20% to about 25% greater than themandrel diameter. In the embodiment illustrated in FIG. 1, the mandrellumen is annular, although other configurations may be used depending onthe shape of the mandrel. The mandrel 32 may have a tapered distal end.

Mandrel 30 may be formed from metallic materials such as stainless steeland nickel titanium alloys, as well as other pseudo-elastic orshape-memory materials, and high modulus polymers such as PEEK , PEl,Nylon, and reinforced composite rod. The inner tubular member 13 andouter tubular member 14 of the catheters of the invention may be formedby conventional techniques, e.g. extruding, from materials already founduseful in intravascular catheters such a polyethylene, polyamide,polyesters and composite materials. The use of the support mandrelallows the use of otherwise soft materials, such as polyamide blockcopolymers, co-polyesters, nylon and polyurethanes, which are compatiblewith materials used to form dilatation balloons. This facilitates thebonding of the outer 14 and inner 13 tubular members to the balloon 24by conventional techniques, such as laser bonding. The cathetercomponents can be bonded together by heat fusion, adhesive, or by otherconventional means.

In certain embodiments, adapter 26 has a third arm (not shown) providingaccess to mandrel lumen 30 so that mandrel 32 may be exchanged to varythe stiffness characteristics of catheter 10 to suit a given procedure.The proximal end of the mandrel 32 would extend out the proximal port inthe third arm, to facilitate exchange of the mandrel. Mandrels havingdifferent flexibilities can be used and the length of the mandrelinserted into the catheter can be adjusted. For example, mandrels madefrom the different mandrel materials listed above, or having differentdiameters, may be exchanged to vary the stiffness of the catheter. Inthe embodiment having an exchangeable mandrel, mandrel lumen 30 ispreferably sealed at the distal end of the lumen 30. Alternatively,mandrel 32 may be fixed within lumen 30, by heat deformation of sidewall28 or with adhesive.

FIGS. 4-7 illustrate alternative embodiments for securing the mandrel 32to the catheter shaft. In the embodiment illustrated in FIG. 4, an outertubular member 34 has a sidewall portion 36 defining a mandrel lumen 32.The sidewall 36 is secured to the outer tubular member 14 along atransverse length of the sidewall 36. Thus, in the embodimentillustrated in FIG. 4, the side wall 36 defining the mandrel lumen 32has an outer diameter which is less than the outer diameter of the innertubular member. FIG. 5 illustrates another embodiment having mandrel 40secured directly to an inner surface of outer tubular member 42, andFIG. 6 illustrates an embodiment having a mandrel 44 secured along itslength to an outer surface of the inner tubular member 46. The mandrel40/44 is secured using adhesive 41 or by heat fusing the polymer shaftto a polymeric mandrel. The mandrel 40/44 is secured along the mandrellength from the proximal end of the mandrel to the distal end of themandrel. Alternatively, the mandrel is secured to the outer tubularmember only at the proximal and the distal ends of the mandrel. FIG. 7illustrates another embodiment having a longitudinally oriented sidewallportion 48 of inner tubular member 50 defining a mandrel lumen 52. Amandrel 54 is contained within lumen 52 and either may be fixed orexchangeable/positionable through an adapter at the proximal end of thecatheter, as discussed above.

FIG. 8, illustrates a prior art over-the-wire catheter having a mandrelwhich is unsecured within the inflation lumen. Such prior art cathetershave poor transfer of axial forces compared to the catheter of theinvention. In the catheter of the invention, the mandrel has improvedtransfer of axial forces, thus allowing the wall thickness of thetubular members to be decreased, and consequently, the size of theinflation lumen for a given diameter catheter to be increased. Theincreased inflation lumen size provides for improved inflation/deflationtimes. The wall thickness of the inner tubular member is typically about0.05 to about 0.2 mm, and the wall thickness of the outer tubular memberis typically about 0.05 to about 0.5 mm, depending on the shaft materialused.

FIG. 9 illustrates another embodiment in which the mandrel may beconfined to an intermediate section of the catheter to provide atransition between the proximal and distal portions of the cathetershaft. In the embodiment illustrated in FIG. 9, catheter 60 generallycomprises inner tubular member 62 having a guidewire port 64 at thedistal end and defining a lumen 66 for slidably receiving guidewire 68,and outer tubular member 70 comprising a proximal portion 72, anintermediate portion 74 and a distal portion 76. Outer tubular member 70is coaxially disposed over inner tubular member 62 creating annularinflation lumen 78. Inflatable member 79 is in communication withinflation lumen 78.

Intermediate portion 74 of outer tubular member 70 is shown in sectionaldetail in FIG. 10 and in cross section in FIG. 11. Generally,intermediate portion 74 comprises a sidewall portion 80 extendinglongitudinally along an inside surface, defining mandrel lumen 82. Amandrel 84 is disposed within lumen 82, providing a transition betweenproximal portion 72 and distal portion 76. By confining the supportmandrel to an intermediate portion of the catheter shaft, less volume ofannular inflation lumen 78 is used by the sidewall 80, leading toimproved inflation and deflation. The mandrel 84 is typically fixedwithin the lumen 82 by raising the temperature of sidewall portion 80 tocause the material to flow into the ends of the lumen 82.

In the embodiment illustrated in FIG. 9, sidewall 80 has a proximal endat the proximal end of the intermediate portion, and a distal end at thedistal end of the intermediate portion. However, the sidewall 80 mayhave a length less than the length of the intermediate section orgreater than the length of the intermediate section when the proximalportion 72 or distal portion 76 has a sidewall defining a mandrel lumenadjacent to lumen 82. The sidewall 80 and mandrel 84 therein aresubstantially shorter than the length of the catheter, i.e., about 5% toabout 20% of the length of the catheter. The length of the sidewall 80is typically about 5 to about 25 cm, preferably about 8 to about 20 cm.The length of the mandrel 84 is about 7 to about 27 cm, preferably about10 to about 22 cm. The length of mandrel 84 may be varied to optimizethe handling characteristics, with ends extending to or beyond thejunctions between the intermediate portion 74 and the proximal portion72 and distal portion 76. In the embodiment illustrated in FIG. 9, themandrel 84 is ground at each end to provide a taper. This smoothes thetransition between materials and minimizes the chances of an end of themandrel puncturing the catheter. The taper extends beyond the ends ofthe lumen 84. In one embodiment illustrated in FIG. 10, the taperedsections of the mandrel begin beyond the ends of the lumen 84. The tapermay extend to the end of the mandrel, or alternatively, a constantdiameter section may be located at each end of the mandrel which extendsfrom an end of the taper to the end of the mandrel. The mandrel may beabout 0% to about 200% longer than the lumen 84, and is typically about10% to about 30% longer than the lumen 84. The mandrel may extend fromeither end of the lumen 84, or from one end, as for example wheremandrel extends only out the distal end of the lumen 84. For a catheterabout 143 cm in overall length, the intermediate portion should be about10 cm, while the support mandrel should be about 22 cm, with about 5 cmof taper at each end. The support mandrel may be about 0.009 inches indiameter when formed from nickel titanium. The proximal portion of thecatheter is about 3.2 F while the distal portion tapers to approximately2.4 F.

Preferably, proximal tubular portion 72, intermediate tubular portion 74and distal tubular portion 76 are dimensioned so that the distal end ofthe mandrel is at, or does not extend beyond, the distal end of theguiding catheter used to introduce catheter 60 into the patient'svasculature. Thus, mandrel 84 supports catheter 60 as it bends throughthe aortic arch and enters the coronary artery. In such embodiments,catheter 60 may exhibit a low stiffness, high stiffness, low stiffnessprofile corresponding to the proximal, intermediate, and distal portionsof the catheter shaft. The intermediate portion 74 is stiffened bymandrel 84, whereas the proximal 72 and distal 76 portions of catheter60 are relatively soft since the guiding catheter can provide supportfor the proximal portion 72 and the distal portion 76 is formed of softmaterial to facilitate advancement in the coronary anatomy However,different characteristics may be obtained easily for differentapplications.

It may be desirable to mark the catheter shaft for fluoroscopicvisualization. However, the sidewall 30/80 does not allow uniformsupport of the tubular member, complicating the use of conventionalmarking techniques. By limiting the sidewall 80 of outer tubular memberto the intermediate portion 74, the proximal portion 72 of outer tubularmember 70 may be marked in a conventional manner. Additionally, theconfiguration provides for improved inflation/deflation times.

As discussed above, the inner and outer tubular members may be formedfrom materials already found suitable for catheter manufacture. In onepreferred embodiment, proximal, intermediate, and distal portions of theouter tubular member are formed of different materials providing aflexibility increasing from the proximal to the distal end of thecatheter. In a presently preferred embodiment, proximal portion 72 isformed from a Nylon blend, the intermediate portion 74 is formed from aNylon, and the distal portion 76 is formed from a polyamide copolymersuch as PEBAX. The inner tubular ember may have proximal, intermediateand distal portions similar to the outer tubular member.

In an alternative embodiment (not shown), intermediate portion 74 doesnot have sidewall 80, and the mandrel 84 is secured directly to theouter tubular member 70 or the inner tubular member 62 at theintermediate portion 74. Preferably, the mandrel 84 is bonded to thetubular member 70/62 with adhesive, although other conventional means ofattachment may also be used. The mandrel 84 can be attached at twopoints adjacent its ends, at intermediate points or along its entirelength. The adhered support mandrel is preferably used with cathetershafts having different materials for the proximal and distal outertubular member portions, to ease the transition between the twomaterials.

In the embodiment illustrated in FIG. 9, intermediate portion 74 is aseparate section joined to the proximal and distal ends of the distal 76and proximal 72 portions, respectively. The intermediate portion 74extends within the proximal 72 and distal 76 portions, although othersuitable joints may be used to join the shaft portions together.Alternatively, the intermediate portion 74 can be eliminated and themandrel 84 may be confined to a location within the proximal end of thedistal portion 76, or the distal end of the proximal portion 72, or itmay extend from the proximal portion 72 to the distal portion 76

In yet another embodiment of the invention, shown in FIGS. 12 and 13,catheter 86 is configured to have rapid exchange capabilities. Generallycatheter shaft 88 comprises an elongated proximal tubular member 90which defines inflation lumen 92. Along an inner surface of proximaltubular member 90 is a longitudinally oriented sidewall portion 94 thatdefines support mandrel lumen 96. A proximal portion of inner tubularmember 98 is adjacent to a distal portion of proximal tubular member.Distal tubular member 100 is coaxially disposed about proximal tubularmember 90 and inner tubular member 98. Accordingly, the proximal end ofdistal tubular member 100 overlaps and seals the proximal portion ofinner tubular member 98 and the distal portion of proximal tubularmember 90 as shown in cross section in FIG. 13. Distal tubular memberdefines a lumen 101 that is in communication with inflation lumen 92.Adapter 102 at the proximal end of catheter shaft 88 provides access toinflation lumen 92. An inflatable member 103 at the distal end of thecatheter is likewise in communication with lumen 101. Inner tubularmember 98 defines guidewire lumen 104 and has a first guidewire port 106at its proximal end and a second guidewire port 108 at its distal endconfigured to receive guidewire 109. Support mandrel 110 is disposedwithin support mandrel lumen 96 and preferably is secured within thelumen but may also be exchangeable.

Suitable materials, such as those already discussed, may be used tofabricate the tubular members of the catheter shaft 88. Generally, thesupport mandrel 110 is configured to give a level of reinforcementequivalent to convention rapid exchange catheters having a proximalhypotube. Presently preferred materials include stainless steel andnickel titanium alloys, with MP35N and 304 stainless steel particularlypreferred. Mandrel 110 should have a length about equal to the proximalportion of the catheter, such as approximately 115 cm for a typical PTCAprocedure. If desired, the distal portion of mandrel 110 can be radiusedor tapered to maximize flexibility without causing kinking at thetransition. Distal end of mandrel 110 can be about 20 to 25 cm from thedistal end of the catheter.

While the present invention is described herein in terms of certainpreferred embodiments, those skilled in the art will recognize thatvarious modifications and improvements may be made to the inventionwithout departing from the scope thereof. Moreover, although individualfeatures of one embodiment of the invention may be discussed herein orshown in the drawings of the one embodiment and not in otherembodiments, it should be apparent that individual features of oneembodiment may be combined with one or more features of anotherembodiment or features from a plurality of embodiments.

What is claimed is:
 1. A catheter for performing an intravascularprocedure, comprising a catheter shaft having a) an inner tubular memberdefining a first lumen; b) an outer tubular member disposed about theinner tubular member to form a second lumen; c) a side wall whichextends inwardly from said outer tubular member and longitudinallywithin the second lumen so as to define a third lumen configured toreceive a mandrel; and d) a mandrel disposed within the third lumen andsecured thereto.
 2. The catheter of claim 1, wherein the mandrel isabout 7 to about 120 centimeters long.
 3. The catheter of claim 2,wherein the third lumen extends to the proximal end of the outer tubularmember.
 4. The catheter of claim 3 wherein the third lumen is about 110to about 125 cm long.
 5. The catheter of claim 1, wherein the mandrel issecured within the third lumen by heat deformation of the sidewall. 6.The catheter of claim 1, wherein the mandrel has a proximal end a distalend and is secured to the outer tubular member at the point adjacent theproximal end of the mandrel and at the point adjacent to the distal endof the mandrel.
 7. The catheter of claim 1, wherein the mandrel has aproximal end, a distal end, and a length extending therebetween, and themandrel is secured to the outer tubular member along the length of themandrel.
 8. A balloon catheter for performing an intravascular procedurecomprising an inner tubular member defining a guidewire lumen and outertubular member disposed about the inner tubular member to define aninflation lumen, wherein the outer tubular member comprises: a) aproximal portion; b) a distal portion having an inflatable member influid communication with the inflation lumen; c) an intermediate portionhaving a sidewall defining a mandrel lumen extending longitudinallyalong an inner surface of the outer tubular member; and d) a mandrel inthe mandrel lumen, wherein the mandrel length is about 25% to about 95%less than a length of the catheter length.
 9. The catheter of claim 8,wherein the mandrel is formed from a material selected from the groupconsisting of stainless steel, nickel titanium PEEK, PEI, nylon, andreinforced composite rod.